Our 4th class pupils made a hovercraft using a balloon , bluetac, a bottle top and a CD Disk. How did they make it? They blew up the balloon. They put bluetac in the top of the balloon and stuck on a bottle top and stuck this to the CD rom. They put it on the floor of the P.E. Hall. As the air came out slowly from the top of the balloon and the balloon and cd rom rose and hovered across the P.E. floor. It was very COOL!